1. Field of the Invention
The present invention relates to control circuits for electronic components, and more particularly, to integrated circuit devices for controlling the operation of motorized ventilation fans for electronics enclosures, and the like.
2. Description of Related Art
Modular ventilation fan assemblies, sometimes called fan tray assemblies (or more briefly, xe2x80x9cTan traysxe2x80x9d) are used for mounting ventilation fans to electronics enclosures, such as computer enclosures. The modular fan trays comprise an electromagnetic interference (EMI) shield, one or more ventilation fans for thermal control of the electronics enclosure, and a control circuit for the ventilation fan or fans. For more efficient manufacturing and assembly, fan trays may be constructed using a common interface design and common components across different designs.
It is often desirable for the fan control circuit to provide a fault signal when predetermined fault conditions are met. Such fault conditions may include a ventilation fan that is missing, electrically disconnected, or otherwise inoperable. Generation of the fault signal permits the fan tray to be replaced before the fault condition causes overheating to occur in the electronics enclosure. In addition, it may sometimes be desirable for a common fan control board to be used with fan trays that incorporate different numbers of fans, for example, a single fan or a pair of fans.
Prior art fan control boards, however, cannot be used for fault detection with different numbers of fans without reconfiguring the boards depending on the number of fans in the fan tray. For example, a prior art board configured for a dual-fan fan tray will generate a fault signal if used in a single-fan fan tray, because the single fan will be interpreted as a fault condition. Conversely, a prior art board configured for fault detection of a single fan only is incapable of reliably signaling the failure of a dual-fan system. Prior art approaches for reconfiguring circuit boards, for example, jumpers, component stuffing options, and switches, do not allow for an identically configured fan control board to be used with fan trays having different numbers of fans. Accordingly, prior art control boards may cause undesirable inefficiencies in manufacturing and assembly.
The present invention provides an interchangeable fan control board, including a fault detection circuit for use with multiple connected components such as ventilation fans, that overcomes the limitations of prior art fan control boards. The fan control board may be used in an identical configuration for different fan tray assemblies containing different numbers of ventilation fans. As such, use of the interchangeable fan control board of the present invention may substantially reduce manufacturing and assembly costs associated with fan trays, while providing fully functional fan control and fault detection.
In an embodiment of the invention, the fan control board is provided with a common electrical connector for connecting the fan tray to other electronics, such as within the electronic enclosure, and a plurality of ventilation fan connectors equal to the maximum number of ventilation fans that the board will control. The ventilation fans for use with the fan control board are provided with a loop back jumper or other passive signaling device according to a logical scheme that disables fault signaling for unused fan connectors on the board.
For example, for a fan control board to be used for both single-fan and dual-fan fan trays, the ventilation fan for the single-fan configuration may be provided with a loop back jumper or other passive signaling device integrated into its fan connection cable. The fan control board, in turn, may be configured to detect when a fan with the passive signaling device is attached to one of the fan connectors, and to disable fault detection for the unused fan connector when such a condition occurs. Conversely, when a single fan for the dual-fan assembly lacking a passive signaling device is attached to the fan control board, the fan control board will signal a fault condition if an operable ventilation fan is not also connected to its second fan connector. Thus, the fan control board may be used interchangeable in an identical configuration with both single-fan and dual-fan fan trays.
The fan control board is anticipated to be particularly effective when the fans for the different fan configurations (e.g., single-fan or dual-fan configurations) are inherently different for reasons unrelated to the presence or absence of a passive signaling device. For example, fans for a single-fan configuration may inherently be a different size, shape, and/or capacity from fans for a dual-fan configuration. If so, the passive signaling devices required for operation of the preferred embodiment of the invention may be provided on ventilation fans without re-introducing any portion of the inefficiencies that are saved by use of the interchangeable fan control board. In the alternative, but less preferably, otherwise identical ventilation fans may be distinguished solely by the presence or absence of a passive signaling device in their cabling and/or connector.
A more complete understanding of the interchangeable fan control board will be afforded to those skilled in the art, as well as a realization of additional advantages and objects thereof, by a consideration of the following detailed description of the preferred embodiment. Reference will be made to the appended sheets of drawings which will first be described briefly.